An automobile fuel including gasoline and the like contains a sulfur component, S, wherein the sulfur component forms sulfur dioxide, SO2 during combustion. For instance, when a catalyst for purifying exhaust gas is under reducing atmosphere, this sulfur dioxide may react with hydrogen, H2 to produce hydrogen sulfide, H2S by a catalytic reaction. Since the resulted hydrogen sulfide can be responsible for strange odors, it is required to suppress production of hydrogen sulfide.
As currently-proposed solutions for suppressing the production of hydrogen sulfide, nickel has been generally added to exhaust gas purification catalysts (Catalysis Today, 9, (1991) 105-112). Japanese Unexamined Patent Publication (Kokai) No. 4-219140 discloses an exhaust gas purification catalyst with a two-layered coating layer, wherein oxidized nickel is added into the layer in order to reduce hydrogen sulfide.
In recent years, however, nickel and nickel compounds are designated by Europe and several other countries as environmental load substances, and thus cannot be used for the catalysts.